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Commissioning dose computation models for spot scanning proton beams in water for a commercially available treatment planning system
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10.1118/1.4798229
/content/aapm/journal/medphys/40/4/10.1118/1.4798229
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/4/10.1118/1.4798229

Figures

Image of FIG. 1.
FIG. 1.

Schematic of the scanning nozzle illustrating its major components.

Image of FIG. 2.
FIG. 2.

(a) IDDs for all 94 energies in units of Gy mm2/MU generated using MC simulations; (b) IDDs values at a depth of 2 cm (MC and measurement) and at the Bragg peak (MC) as a function of proton energy; the inset is MC-generated CFs at a depth of 2 cm; and (c) FWHM of Bragg peaks (MC) in the depth direction as a function of proton energy.

Image of FIG. 3.
FIG. 3.

MC simulation-generated lateral in-air dose profiles at different positions (z = 0, ±10, ±20 cm, z = 0 is defined at the isocenter). (a) For all energies; (b) for the pencil beam with energy of 221.8 MeV; and (c) σ 1 and σ 2 in the plane of isocenter (z = 0) versus energy.

Image of FIG. 4.
FIG. 4.

In-air lateral profiles for pencil beams with three different energies. Solid lines: MC; dots: measured data; dashed lines: calculated by SG fluence model; dashed-dotted lines: calculated by DG fluence model with empirical parameters; and dashed lines: calculated by DG-EFP. (a) 72.5, (b) 148.8, and (c) 221.8 MeV.

Image of FIG. 5.
FIG. 5.

Comparisons between calculated (SG, DG-EFP, and DG fluence models) and measured FSFs of square fields. Positive values in percentage differences represent calculated FSFs larger than measured ones. For FSFs, dotted-dashed lines: SG; dashed lines: DG-EFP; solid lines: DG; and squares: measured. For percent differences, dotted-dashed lines with circles: SG; dashed lines with triangles: DG-EFP; and solid lines with diamonds: DG. (a) and (b) for energy of 72.5 MeV (4.0 cm range) at depths of 2.0 and 3.7 cm; (c) and (d) for energy of 148.8 MeV (15.2 cm range) at depths of 2.0 and 15.0 cm; (e)–(g) for energy of 221.8 MeV (30.6 cm range) at depths of 2.0, 30.0, and 23.2 cm, respectively.

Image of FIG. 6.
FIG. 6.

Percentage differences between the calculated (by DG fluence model) and measured FSFs for 20 monoenergetic fields at two depths as a function of field size (a) and proton energy (b). Positive values in percentage differences represent calculated FSFs larger than measured ones.

Image of FIG. 7.
FIG. 7.

Percent differences between calculated (by both SG and DG fluence models) and measured doses at the center of the field and SOBP (4 cm) as a function of field size for three different proton ranges, 10.5, 20.0, and 30.6 cm. Positive values represent calculated doses larger than measured ones. (a) SG fluence model; (b) DG-EFP; and (c) DG fluence model with empirical parameters.

Image of FIG. 8.
FIG. 8.

Percentage differences between doses calculated by the DG fluence model and those measured at the center of the field and the SOBP as a function of field size (a) and range (b). The SOBP widths range from 2 to 24 cm. Positive values in percentage differences represent calculated doses larger than measured ones.

Image of FIG. 9.
FIG. 9.

Comparison of the depth doses calculated using the DG fluence model and measurements along the central axis of proton fields with the nominal field size of 10 × 10 cm for four different proton ranges with SOBP width of 10 or 4 cm.

Image of FIG. 10.
FIG. 10.

Comparison of the DG, SG fluence models calculated and measured inplane lateral dose profiles at the center of the SOBP for four different proton ranges and SOBP widths of 10 or 4 cm. Dots: measured data; solid lines: calculated by the DG fluence model; dashed lines: calculated by the SG fluence model. (a) Range = 30.6 cm, SOBP = 10 cm; (b) range = 20.5 cm, SOBP = 10 cm; (c) range = 12.1 cm, SOBP = 4 cm; and (d) range = 8.1 cm, SOBP = 4 cm.

Image of FIG. 11.
FIG. 11.

Clinical examples of comparison of depth doses between measured and calculated by the DG and SG fluence models. Diamonds: measured; solid lines: calculated by the DG fluence model; and dashed lines: calculated by the SG fluence model. (a) and (b) are for a patient with prostate cancer treated with right and left lateral fields. The depth doses were recalculated with the DG fluence model for the original plan which was optimized and calculated with the SG fluence model as the dose model; (c) and (d) are for two of four fields for a pediatric patient with chordoma in the base of skull. The patient plan was optimized and calculated with the DG fluence model and the SG depth doses were recalculated with SG fluence model for the purpose of comparison.

Image of FIG. 12.
FIG. 12.

Clinical examples of comparison of isodose distributions between measured and calculated by the DG [(a) and (c)] and SG [(b) and (d)] fluence models, respectively. Solid lines: measured isodose lines; and dashed lines: calculated isodose lines. (a) and (b) are for a right lateral prostate field at the depth of 18.4 cm; (c) and (d) are for one of the vertex field [the same field as in Fig. 11(d) ] at a depth of 11.9 cm.

Tables

Generic image for table
TABLE I.

Values of DDNT at selected energies/ranges for the DG fluence model. The ideal value of DDNT = 1/1.1 = 0.9091. The percentage difference is the difference in percent between DDNT values used by the DG fluence models and the ideal value.

Generic image for table
TABLE II.

Comparison of dosimetric parameters of lateral dose profiles in water presented in Fig. 10 .

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/content/aapm/journal/medphys/40/4/10.1118/1.4798229
2013-04-02
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Commissioning dose computation models for spot scanning proton beams in water for a commercially available treatment planning system
http://aip.metastore.ingenta.com/content/aapm/journal/medphys/40/4/10.1118/1.4798229
10.1118/1.4798229
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